Copper(II) sulfate most commonly exists as the blue pentahydrate CuSO₄·5H₂O
CHEMISTRY · Multi-part · A Level · Chemistry · Amount of substance · Amount of substance
Problem
Copper(II) sulfate most commonly exists as the blue pentahydrate CuSO₄·5H₂O. A teacher asks a student to prepare 500.0 mL of 0.150 mol L⁻¹ aqueous CuSO₄ (not CuSO₄·5H₂O) for an electrochemistry experiment. Only the crystalline pentahydrate is available.
(a) Calculate the mass of CuSO₄·5H₂O, in grams, that the student must dissolve to obtain the required solution.
(b) While the solid is dissolving, 5.0 mL of water is lost from the beaker by evaporation. Assuming no copper(II) sulfate is lost, determine the molarity of CuSO₄ in the partially evaporated solution.
(c) After the solution is transferred to a 500 mL volumetric flask, the student adds distilled water up to the calibration mark. Explain quantitatively whether the final molarity of CuSO₄ will exactly match the teacher’s specification, taking into account both the lost water in part (b) and the uncertainty in measuring solid mass (±0.01 g). Show all supporting calculations and state any assumptions.